1. Field of the Invention
The present invention relates to a wet electrographic printer, and more particularly, to a developer supply method of controlling the concentration and level of the developer in a wet electrographic printer.
2. Description of the Related Art
In general, a wet electrographic printer develops an electrostatic latent image formed on a photosensitive medium, such as a photosensitive belt, with a developer of a predetermined color, and transfers the developed image to a paper sheet. A developing unit applies developer to the photosensitive medium to develop the electrostatic latent image formed thereon, and a developer supply apparatus supplies developer of a predetermined density to the developing unit. The developer comprises a condensed ink containing a toner mixed with a liquid carrier. The developer includes the toner diluted to approximately 2-4 wt %. Hereinafter, the wt % of toner is referred to as the concentration of the developer.
The developer supply apparatus includes an ink cartridge for storing the condensed ink, a carrier cartridge for storing the liquid carrier, and a reservoir for storing the developer obtained by mixing the condensed ink with the liquid carrier at a predetermined ratio. Agitators, for preventing the toner from settling, may be installed in the ink cartridge and the reservoir.
Since developer stored in the reservoir is used to develop the electrostatic latent image formed on the photosensitive medium, the condensed ink and the liquid carrier must be supplied to the reservoir to maintain a predetermined developer concentration. Also, the developer stored in the reservoir must be replenished.
The consumption of toner and liquid carrier varies depending on the images printed. For example, more liquid carrier than toner is consumed to print a simple image or a small image; while more toner than liquid carrier is consumed to print a complicated image. Thus, in order to maintain the predetermined developer concentration, it is necessary to appropriately supply the toner and the liquid carrier to the reservoir in accordance with the consumption of the toner and the liquid carrier, respectively.
Conventional developer supply methods cannot control both the concentration and level of the developer stored in the reservoir. That is, if a lot of the liquid carrier is supplied to maintain the predetermined developer concentration, the level of the developer changes. Thus, undesired operating conditions may develop. On the other hand, if the level of the developer is controlled, the predetermined developer concentration can not be maintained.